Facile synthesis of new, highly efficient SnO2/carbon nitride composite photocatalysts for the hydrogen evolution reaction

Novel SnO2/carbon nitride photocatalysts having surface areas up to 220 m(2) g(-1) were prepared for the first time by condensation of dicyandiamide in alkali metal chloride/SnCl2-containing salt melts at 550 degrees C, without the use of hard templates. XRD and HR-TEM investigations showed that the obtained materials are composed of 5-10 nm SnO2 nanoparticles deposited onto nanosheets set up from 1D-melon ribbons. The morphology and crystalline structure of products appear to be greatly dependent on the synthesis temperature. SnO2/carbon nitride composites are found to be highly efficient in the photocatalytic reactions, as exemplified by Rhodamine B degradation and water reduction using Pt as a cocatalyst. Under the optimized synthesis conditions, these composite photocatalysts achieve hydrogen evolution rates more than 2 times higher than the mesoporous carbon nitride (mp-CN) under visible light irradiation. In principle, this new method based on utilization of MCl/SnCl2 salt melts as a reaction medium allows carrying out various polymerization reactions in the presence of the mild Lewis acid in the solution phase in the wide temperature range of 180-550 degrees C. Moreover, SnCl2 eutectics are even suitable for post-synthesis modification of the bulk carbon nitride to tune its morphology and greatly increase the surface area and photocatalytic activity.